Magnetic head and method of making same



p i 1954 F. G. BUHRENDORF v 2,574,659

MAGNETIC HEAD AND METHOD OF MAKING SAME Filed Nov. 2, 1951 2Sheets-Sheet 1 FIG.

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INVENTOR By F. G. BUHRENDORF VV-QQM A T TOR/LIE V April 6, 1954 F. G.BUHRENDORF 2,674,659

MAGNETIC HEAD AND METHOD OF MAKING SAME Filed Nov. 2, 1951 2Sheets-Sheet 2 FIG. 4

- FIG. 5 FIG. 5 2

/4 v v l2 INVENTOR F. G. BUHRENDORF A TTORNE V Patented Apr. 6, 1954MAGNETIC HEAD AND METHOD OF MAKING SAME Frederick G. Buhrendorf,Westfield, N. .L, assignor to Bell Telephone Laboratories, Incorporated,New York, N. Y., a corporation of New.

York

Application November 2, 1951, Serial No. 254,537

7 Claims. 1

This invention relates to magnetic heads for use in magnetic recording,reproduction or obliteration.

The object of the present invention is to provide a magnetic head ofstable design, which is suitable for high frequency recording and eprduc n In accordancewith the general features of this invention amagnetic core comprising one or more laminations of high permeabilitymagnetic material, such as Permalloy, is wound around a ceramic wafertriangularly shaped at one end and notched at two opposite sides. Acoil, space wound on a ceramic form, is mounted adjacent each of saidnotched sides. The magnetic core is threadedlthrough each of said coilsand disposed between the triangular sides of said ceramic wafer and alow resistancemetallic shield to form two pole tips. The entire assemblyis coated with a ceramic material and fired to. form a glazed coating.The pointed end of the wafer is then ground and lapped until the desiredseparation of the pole tips is obtained.

The coating of the magnetic head with a ceramic glaze provides a rigidlyclamped pole tip assembly held permanently. in adjustment once properlylapped.

The nature of the invention and its distinguishing features andadvantages will be more clearly. understood from the. following detaileddescription and the accompanying drawings in which:

Fig.1 is a view in front elevation of the assembled magnetic, head;

Fig, 2is a sectional view taken on the line 2-2 of Fig, 1;

Fig. 3 is. a sectional view taken on the line 3-3 of Fig. 1;

Fig. 4 is a View in perspective partially expanded to show thestructural features of the head components;

Fig. 5 is a sectional view taken on the line 5-5 of Fig. 1; and

Fig. 6 is a view in front elevation showing the actual dimensions of themagnetic head.

Referring now to the embodiment of the present invention shown in theaccompanying drawings, 2 is a ceramic wafer triangularly shaped at oneend and notched at two opposite sides. The ceramic forms 4, about whichthe recording and reproducing coils 6 are wound, are mounted adj acentthe notched sides of the wafer 2 and are held in position by means ofthe notched portions 8 and the magnetic core l0 which is wound aroundthe water 2 and threaded through each of the forms 4 and the coils B.The ends of the magnetic core W are disposed between the triangularsides of the wafer 2 and a low resistance, nonmagnetic shield l2 whichis held in position adjacent the wafer 2 by means of the ceramic pin l4.

The shield l2 may be made of a material such as copper. The core II),which may be in the form of a ribbon having a thickness of 0.001 inch,is made ofmagnetic material, such as Permalloy. The surface of theribbon is coated with a layer of suitable inert insulating material,such as Alundum in order to prevent metal contact between the core 10and the shield l2 or the terminal wires It. The terminal wires IS, thecoils 6 and the wires l8 which connect the coils 6 in series arepreferably of tungsten. The terminal wires l6 and the connecting wires18 are Welded to the coils 6. The triangularly-shaped wafer 2 and theforms 4- may be made of a material such as steatite.

.As shown in Fig. 4, the ceramic forms 4 comprise .a male portion 20 anda female portion 22 which, when joined and held together by the coil 6,support the wires I6 and I8.

After the magnetic head is assembled, as shown in Fig. 1, it is coatedwith a ceramic material and fired. The ceramic coating should be soselected that the firing temperature of the coating coincides with theheat treating temperature of the magnetic core so that the glazing willbe completed simultaneously with the heat treatment of the magneticmaterial. A ceramic material consisting of the following componentshasbeen found to be satisfactory for this purpose when Permalloy isemployed as the magnetic material:

Parts by weight Sodium oxide 11.2 Potassium oxide 5.0 Boron oxide 13.0Aluminum oxide 8.1 Silicon dioxide 55.3 Calcium fluoride 4.2 Cobaltoxide 2.4 Lithium oxide -i 0.8

The heat treatment of the magnetic core after assembly is a desirablefeature since it avoids handling of the core after heat treatment, aprocedure which is known to lower the magnetic qualities of thinPermalloy laminations.

After the magnetic head assembly has been fired, the unwanted ends ofthe magnetic core or ribbon ID are clipped and the pointed end of theentire assembly, including the shield I2, is ground.

and/or lapped until the desired separation of the pole tips 24 and 28 isobtained. The magnetic head unit may be mounted on its associatedequipment by means of the mounting holes 28 in the shield [2.

It is to be understood that the above-described arrangements areillustrative of the application of the principles of the invention.Other arrangements may be devised by those skilled in the art withoutdeparting from the spirit and scope of the invention.

What is claimed is:

l. A magnetic recording-reproducing head coated with a ceramic glaze andcomprising a ceramic member two opposite sides of which converge to forma point at one end, an eddy current shielding member disposed about thepointed end of said ceramic member, and a ribbon of magnetic materialwound around said ceramic member and disposed between the convergingsides of said ceramic member and said shielding member to form two poletips spaced by the pointed end of said ceramic member, said ceramicmember, said shielding member and said ribbon being fixedly positionedby means of said glazed ceramic coating.

2. A magnetic recording-reproducing head coated with a ceramic glaz andcomprising a ceramic wafer triangularly shaped at one end, an energizingcoil wound on a ceramic member disposed adjacent said ceramic waier, aneddy current shielding member disposed about the triangularly-shapedportion of said ceramic wafer, a core comprising a thin lamination ofmagnetic material disposed around said ceramic wafer and threadedthrough said ceramic member and said coil, the ends of said core beingdisposed between the triangular sides of said ceramic wafer and saidshielding member to form two spaced pole tips, said ceramic wafer, saidenergizing coil, said shielding member and said core being fixedlypositioned by said glazed ceramic coating.

3. A magnetic recording-reproducing head coated with a ceramic glaze andcomprising a ceramic Wafer two opposite sides of which converge to forma point at one end, a pair of energizing coils, each of said coils woundon a ceramic member, said ceramic members being disposed adjacent saidopposite sides of said ceramic wafer, an eddy current shielding memberdisposed about the pointed end of said ceramic wafer, a ribbon ofmagnetic material disposed around said ceramic wafer and threadedthrough said ceramic members and said coils, the ends of said ribbonbeing disposed between the converging sides of said ceramic wafer andsaid shielding member to form two spaced pole tips, said ceramic wafer,said energizing coils, said shielding member and said ribbon beingfixedly positioned by said glazed ceramic coating.

4. A magnetic recording-reproducing head coated with a ceramic glaze andcomprising a ceramic wafer triangularly shaped at one end, a pair ofserially connected coils, each of said coils wound on acylindrically-shaped ceramic member, said cylindrically-shaped membersbeing disposed adjacent opposite sides of said wafer, an eddy currentshielding member disposed about the triangularly-shaped portion of saidwafer, a core comprising a. thin lamination of magnetic materialdisposed around said wafer and threaded through saidcylindrically-shaped ceramic members and said coils, the ends of saidcore being disposed between the triangular sides of said wafer and saidshielding member to form two spaced pole tips, said wafer, saidcylindricallyshaped ceramic members, said shielding member and said corebeing fixedly positioned by means of said glazed ceramic coating.

5. A magnetic recording-reproducing head comprising a core of magneticmaterial, said head being coated with a ceramic glaze, said magneticmaterial having an annealing temperature coinciding with the firingtemperature of said ceramic coating.

6. A magnetic recording-reproducing head coated with a ceramic glaze andcomprising a ceramic wafer two opposite sides of which converge to forma point at one end, said opposite sides having notched portions, a pairof serially connected energizing coils, each of said coils wound on acylindrically-shaped ceramic member, said ceramic members being disposedwithin the notched portions of said opposite sides of said ceramicwafer, an eddy current shielding member disposed about and secured tothe pointed end of said ceramic wafer, a ribbon of magnetic materialdisposed around said ceramic wafer and threaded through saidcylindrically-shaped ceramic members and said energizing coils, the endsof said ribbon of magnetic material being disposed between theconverging sides of said ceramic wafer and said shielding member to formtwo spaced pole tips, said ceramic wafer, said energizing coils, saidshielding member and said ribbon of magnetic material being fixedlypositioned by said glazed ceramic coating.

7. A magnetic recording-reproducing head in accordance with claim 6wherein the annealing temperature of the ribbon of magnetic materialcoincides with the firing temperature of the ceramic coating.

References Cited in the file of this patent UNITED STATES PATENTS

